The invention relates to a method for transmitting data packets based on the Ethernet transmission protocol between at least one mobile communication unit and a communication system.
Existing communication systems or mobile radio systems have for example a communication network (“core network”) to which individual mobile communication terminals are connected via “access networks”. Among the services made available in mobile radio systems of said kind, packet-oriented communication services are also provided. In addition to the “General Packet Radio Service” (GPRS) access technology, packet-oriented communication services are provided within the mobile communication system by way of further access technologies such as, for example, the “Worldwide Interoperability for Microwave Access” (WIMAX) technology.
Of particular importance in the context of packet-oriented data transmission is the Internet Protocol (IP) transmission protocol, which enables individual data packets to be switched via different transmission systems by cross-network addressing based on what are referred to as IP addresses. Version 4 of the Internet Protocol (IPv4), which has a 32-bit address system and theoretically supports an address space of up to four billion IP addresses, is currently the most widespread. In practice, however, a large proportion of these addresses cannot be used due to group forming and other mechanisms. Consequently, owing to the constantly growing number of Internet users it is necessary to create IP addresses with a larger address space. Toward that end, work has been in progress for several years on a version 6 of the Internet Protocol (IPv6). The new IPv6 has, for example, a considerably larger address space on account of a 128-bit address system. This increases the number of potentially available IP addresses many times over.
An extension to the traditional Internet Protocol is the Mobile Internet Protocol, also called Mobile IP or MIP, which enables data packets to be transported beyond mobile communication network boundaries. A distinction is made here between versions MIPv4 and MIPv6, which supported the different versions 4 and 6, respectively, of the IP transmission protocol. The Mobile IP transmission protocol in combination with version 4 of the Internet Protocol (IPv4) is in use at the present time. Three new functional entities have been defined in connection with the Mobile IP transmission protocol (RFC 3344): mobile network node, home agent and foreign agent:
A mobile network node, or “mobile node” (MN), is understood to mean a computer unit which can change its access point in the mobile communication system and in the process maintains an existing data connection and only uses an IP address for the purpose of unique identification.
A home agent (HA) is a router/computer unit having an interface to the home communication network of the mobile network node. It is notified by the mobile network node of the latter's current location, receives data packets addressed to the mobile network node and forwards these packets to the mobile network node.
The term “foreign agent” (FA) is used to describe a router/computer unit in the foreign communication network which forwards data packets to the mobile network node and serves as a standard router unit for data packets generated by the mobile network node.
Each mobile node possesses two addresses: a home address and what is referred to as a “care-of address”. The home address is the IP address by which the mobile network node is known to its communication partners. It is “permanently” assigned to the mobile node and remains fixed even when, for example, the mobile network node roams in the mobile communication network. The front part of the home address, which specifies the network, is identical to the network prefix which the host and router units possess in the home communication network of the mobile network node.
The care-of address (COA) is an IP address which is used as a temporary address by a mobile network node when it visits a foreign communication network. It is specific to the foreign communication network and changes as soon as the mobile network node visits a new foreign communication network. The care-of address therefore defines the location of the mobile network node and represents the address to which the data packets addressed to the mobile network node are forwarded.
Also known from the RFC 1701 and 1702 standards is the “Generic Route Encapsulation” (GRE) transmission protocol, wherein in conjunction with the “Point-to-Point Tunneling Protocol” (PPTP) a tunnel connection is set up between, for example, a virtual private communication network (VPN) and a client or between a plurality of clients or between clients and server unit. For this purpose the encrypted useful load (“payload”) is inserted into a GRE data packet and transferred between the endpoints via a transport protocol of the tunnel. Following this, the further switching of the data packet transmitted via the tunnel to the recipient takes place using a “normal” transmission protocol such as, for example, the IP transmission protocol. For this purpose, according to the GRE transmission protocol a key field is provided in which a GRE key is stored via which the data packet is identified.
An extension to the Mobile IPv4 transmission protocol for the purpose of exchanging GRE keys is known from the Internet publication “GRE Key Extensions for Mobile IPv4” by Parviz Yegani et al, IETF Mobile IP Working Group. In this, a method for setting up a tunnel connection between a foreign agent and a home agent is described wherein the configuration of the home agent executing the Mobile IPv4 transmission protocol can be maintained unchanged and at the same time overlaps in the IPv4 address range are avoided.
In the mobile communication network, the foreign agent is additionally assigned an Access Service Network Gateway (ASN-GW) unit, and the home agent a Connectivity Service Network (CSN) unit. In this case the foreign agent and the home agent are connected to each other via an interface provided with the identifier R3. According to the current standardization status, although the IPv4 and IPv6 data transmission protocols are supported by the at least partially standardized R3 interface, the Ethernet data transmission protocol is by no means supported simultaneously.